As more and more applications reside on MEMS it will be useful to have two different MEMS for different MEMS processes connected to a CMOS to provide electronic circuits. This is particularly useful where the two different MEMS processes may require different environments to function efficiently. For example, pressure sensors, chemical sensors, sound sensors and the like may need access to the ambient environment; as opposed to accelerometers and gyroscopes, which need hermetically sealed chambers since they require specific pressure for optimal performance. Combining a MEMS, a CMOS and another MEMS in one package that is vertically stacked results in a smaller package with reduced requirements for board area or “real estate.”
Controlling stress in the MEMS is another issue that needs to be addressed. Stress/strain in the substrate on which a sensor is mounted or integrated causes the performance of the sensor to change.
Accordingly, it is desired to have a device that addresses the requirements of two different MEMS for different MEMS processes in a single package as well as stress isolation. The present invention addresses such a need.